An open cuboidal box (no top) measures 10 cm × 8 cm × 5 cm. Find the area of cardboard needed to make it (5 faces only).

Class 8MensurationMensuration

Step-by-Step Solution

TSA =

2 (l b + bh + h l) = 2 (80 + 40 + 50) = 340 cm^{2}

. Remove one top face

(l \times b = 10 \times 8 = 80 cm^{2}) : 340 - 80 = 260 cm^{2}

Answer: C) 260

A cuboid has 3 pairs of identical opposite faces. Their total area:

- 2 faces of

l \times b

(top + bottom)
- 2 faces of

b \times h

(front + back)
- 2 faces of

l \times h

(left + right)

**TSA of cuboid =

2 (l b + bh + h l)

.**
**LSA of cuboid =

2 h (l + b)

** — only the four side walls, used for room painting (not floor/ceiling).

Special case (cube,

l = b = h = s

): TSA =

6 s^{2}

, LSA =

4 s^{2}

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